Method and anchor for medical implant placement, and method of anchor manufacture

ABSTRACT

An anchor and procedure for placing a medical implant, such as for monitoring physiological parameters. The anchor includes a central body in which a medical implant can be received. Arms and members extend radially from first and second ends, respectively, of the central body. Each member defines a leg extending toward distal portions of the arms to provide a clamping action. The anchor and its implant are placed by coupling first and second guidewires to first and second portions of the anchor, placing an end of a delivery catheter in a wall where implantation is desired, inserting the anchor in the catheter with the guidewires to locate the anchor within the wall, deploying the arms of the anchor at one side of the wall followed by deployment of the members at the opposite side of the wall, and thereafter decoupling the guidewires from the anchor.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a division patent application of co-pending U.S. patentapplication Ser. No. 10/898,053, filed Jul. 24, 2004, which claims thebenefit of U.S. Provisional Application Nos. 60/489,974, filed Jul. 25,2003, and 60/491,002, filed Jul. 30, 2003, the contents of which areincorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

This invention was made with Government support under Contract No.NNC04CA10C awarded by National Astronautics and Space Agency. TheGovernment has certain rights in the invention.

BACKGROUND OF THE INVENTION

The present invention relates generally to implantable medical devices,such as of the types for monitoring physiological parameters. Moreparticularly, the invention relates to an anchor for a medical implant,a method of manufacturing anchors, and a method of placing a medicalimplant, wherein the anchor and method are suitable for use inprocedures performed to diagnose, monitor, and/or treat cardiovasculardiseases, including procedures performed to monitor pressure in the leftside of the heart.

Congestive Heart Failure (CHF), a condition in which the heart fails topump efficiently, currently affects about 4.7 million patients (over400,000 new patients per year in the U.S.), accounts for about 5 to 10%of all hospitalizations, and costs over $38 billion in the U.S.Following diagnosis of congestive heart failure, physicians typicallymonitor disease progression on a continuing basis to better tailortreatment. The best course of action for a tailored treatment involvesmonitoring of the pressures of the left side of the heart, particularlyleft ventricular end diastolic pressure (LVEDP, also known as leftventricular filling pressure) and mean left atrium pressure (MLA). Thesepressures are recognized as the best parameters for characterizingcongestive heart failure in patients. Clinical evaluation of LVEDP orMLA is currently limited to a cardiac catheterization procedure, whichprovides a snapshot of pressure data a few times per year at most,carries morbidity, and is expensive.

Monitoring the pressures of the left side of the heart is a verychallenging task for many reasons, most importantly the potentiallyfatal outcome of any thrombi caused by the implant. Implants can be madeusing many technologies, though preferred methods typically include MEMS(Microelectromechanical systems) devices and technologies. Suchminiaturized implants can provide chronic, continuous bio-pressuremeasurements and support the trend toward home health monitoring.Pressure monitoring systems have two primary components: the implantcomprising an implantable telemetric pressure sensor that is batterylessor makes use of a small battery, and a companion hand-held reader. Theimplant further includes custom electronics for processing the output ofthe sensor and an antenna for telemetry and, if necessary or desired,for tele-powering the sensor. Telemetry and tele-powering can beachieved via various techniques, including but not limited to magnetictelemetry (including RF), acoustic waves, ultrasonic waves, with thecurrently preferred technique typically being magnetic telemetry. Thereader transmits power to the sensor, and the sensed pressure is in turntransmitted back to the reader. Data collected from the sensor can thenbe used by a physician to tailor the treatment of the patient. In somecases, the implant may also be configured or adapted to performadditional functions, such as delivering a drug or an electric signal tothe muscles/nerves.

Though the above evidences that significant advances have been achievedfor implants capable of diagnosing, monitoring, and/or treatingcardiovascular diseases, further improvements are desired, particularlypertaining to the delivery and anchoring of such medical implants withinthe heart for monitoring heart pressures.

BRIEF SUMMARY OF THE INVENTION

The present invention provides an anchor for a medical implant, a methodof manufacturing the anchor, and a procedure for placing a medicalimplant such as for monitoring physiological parameters. The inventionis particularly directed to implantation of physiologicsensors/actuators for diagnosing and/or monitoring and/or treatingcardiovascular diseases, such as congestive heart failure and congenitalheart disease.

The anchor of this invention includes a central body in which a medicalimplant can be received. The central body has an axis and first andsecond ends in oppositely-disposed first and second directions,respectively, along the axis of the central body. A plurality of arcuatearms extend substantially radially from the first end of the centralbody, and each arcuate arm has a distal portion extending in the seconddirection relative to the central body. A plurality of arcuate membersextend substantially radially from the second end of the central body,and each arcuate member defines a leg extending in the first directiontoward the distal portions of the arcuate arms. The anchor can befabricated so that two or more of the its components are integralportions as a result of being machined, preferably laser cut, from amonolithic body.

The anchor makes possible a method for placing a medical implant. Such amethod involves coupling at least a first guidewire to a first portionof an anchor in which the medical implant is received and coupling atleast a second guidewire to a second portion of the anchor. An end of adelivery catheter is then placed within an opening in an internal wallof a human body, and the anchor is inserted in the delivery catheterwith the first and second guidewires so as to place the anchor withinthe internal opening of the body. The anchor is inserted so that aplurality of arcuate arms extending substantially radially from thefirst portion of the anchor are released from the end of the deliverycatheter. The first and second guidewires are then retracted through thedelivery catheter so that the arcuate arms of the anchor contact a firstside of the internal wall. Thereafter, the delivery catheter can beretracted to release a plurality of arcuate members extendingsubstantially radially from the anchor. Each arcuate member defines aleg contacting an oppositely-disposed second side of the internal wallso as to secure the anchor and the medical implant received therein tothe internal wall. Finally, the second guidewire is decoupled from thesecond portion of the anchor, and the first guidewire is decoupled fromthe first portion of the anchor.

In view of the above, it can be seen that the present invention providesan uncomplicated anchor and procedure of placing an implantable medicaldevices for monitoring physiological parameters. The configuration ofthe anchor addresses delivery issues, including delivery method,delivery equipment, implant design, and anchor location, that arise whenemploying implantable physiologic sensors/actuators to diagnose and/ormonitor and/or treat cardiovascular diseases such as congestive heartfailure and congenital heart disease. Notably, the anchor and itsdelivery find application in very challenging application of monitoringthe pressure of the left side of the heart. Medical implants that can beplaced and anchored in accordance with this invention can operatewirelessly or can be connected to other devices (such as pacemakers)using electrical wires (e.g., pacemaker leads, polymer based flexcables, or wires) or other types of communications means (e.g.,ultrasonic, optical, or electrophysiology signals).

Other objects and advantages of this invention will be betterappreciated from the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 through 3 are perspective, side, and end views, respectively, ofan anchor for a medical implant in accordance with an embodiment of thisinvention.

FIG. 4 is a cross-sectional view showing a medical implant anchored to awall with the anchor of FIGS. 1 through 3.

FIG. 5 is a perspective view showing the use of a delivery catheter andtwo guidewires in the process of placing the anchor and medical implantin a wall in accordance with FIG. 4.

FIG. 6 is a perspective view of a preform from which the anchor of FIGS.1 through 3 can be fabricated.

FIGS. 7 and 8 are side and cross-sectional views, respectively, showingan assembly comprising the delivery catheter, guidewires, anchor andmedical implant of FIG. 4.

FIGS. 9 through 14 are perspective views representing procedural stepswhen placing the anchor and medical implant.

FIG. 15 is a cross-sectional view showing a medical implant anchored toa wall with an anchor in accordance with a second embodiment of thisinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 through 5 depict an anchor 10 suitable for delivering andsecuring a medical implant 12 to a wall 14, such as a wall of acardiovascular organ, in accordance with an embodiment of the presentinvention. In a notable example, the wall 14 is an atrial septum and theimplant 12 measures physiological parameters of the heart, such as LVEDPor MLA pressure. The implant 12 may be any one of a variety of types ofimplants currently known or developed in the future, and the scope ofthe present invention is not limited in any way by the type andoperation of the implant 12.

The anchor 10 is represented in the Figures as having an annular-shapedcentral body 16 that defines a bore 17 in which the implant 12 isreceived. The central body 16 has oppositely-disposed first and secondends 18 and 20 corresponding to oppositely-disposed first and seconddirections along the axis of the central body 16. Arcuate arms 22 extendsubstantially radially and in the first direction from the first end 18of the central body 16, and arcuate members 24 extend substantiallyradially and in the second direction from the second end 20 of thecentral body 16. As can be seen from FIG. 3, each arm 22 and arcuatemember 24 lies in a plane containing the axis of the central body 16. Asalso evident from FIG. 3, each arm 22 is axially aligned with one of thearcuate members 24 so as to lie in the same plane as the arcuate member24.

Each arm 22 has a distal portion extending in the second directionrelative to the central body 16, terminating in a pad 26 orientedsubstantially transverse to the axis of the central body 16. Eacharcuate member 24 defines a leg 28 that extends in the first directiontoward the pads 26 of the arms 22, and has a distal portion 30 thatextends in the second direction from its respective leg 28. As a resultof the arms 22 and arcuate members 24 being axially aligned with eachother, the pads 26 of the arms 22 oppose the legs 28 of the arcuatemembers 24, such that the pads 26 and legs 28 cooperate to clamp thewall 14 as seen in FIG. 3, such that the anchor 10 is able to resistaxial and rotating forces that might dislodge the anchor 10 and itsimplant 12. The pads 26 are depicted as having ring-shapes to helpdistribute the clamping force across a larger area of the wall 14 andpromote the overall stability of the anchor 10, though other shapes andconfigurations are foreseeable for the pads 26. As will be evident fromthe following description of the implantation procedure, the circularshape of the pads 26 also helps prevent dead-ending during delivery inthe anchor 10 and its implant 12. In addition to the arms 22 and arcuatemembers 24, the anchor 10 may include a mesh (not shown) to promotetissue growth and anchoring.

The arcuate members 24 support a first ring 32 at their distal portions30, such that the ring 32 is axially spaced from the second end 20 ofthe central body 16. A second ring 34 is axially spaced from the secondend 20 of the central body 16 so as to be located between the centralbody 16 and the first ring 32. A number of struts 36 extend from thesecond end 20 of the central body 16 to secure the second ring 34 to thecentral body 16. As evident from FIG. 4, the implant 12 is placed withinthe central body 16 and a cage defined by the struts 36. One end of theimplant 12 abuts the second ring 34, while the opposite end of theimplant 12 is secured to the central body 16 with fingers 38 that arecrimped over the opening of the bore 17 in which the implant 12 isreceived to retain the implant 12 within the anchor 10. The fingers 38can be initially formed to be open or temporarily moved away to allowthe implant 12 to be placed inside the bore 17 of the central body 16.This low-profile configuration minimizes the diameter required of acatheter (44 in FIG. 5) used to delivery the anchor 10 and implant 12,and advantageously results in the anchor 10 exerting minimal stress onthe implant 12.

The first and second rings 32 and 34 are adapted to enable guidewires 40and 42 to be coupled to the anchor 10, as seen in FIGS. 5, 7, and 8.Coupling of the guidewires 40 and 42 to the rings 32 and 34 can beaccomplished in different ways including without limitation one, more,or any combination of the following methods: cam slot, threading,snapping, snap latch, latch fingers, spring latch, latch fingers with acatheter sheet on top to release the latch, use of one or moreguidewires or catheters in order to either latch or release couplingmeans (such as latching fingers), dissolvable glues, temporary glues,thermal glues, heated shape memory latches, unheated shape memorylatches, heated mechanical means, piezoelectric release system,hydraulic coupling systems, pneumatic coupling systems, magneticcoupling systems, etc. In the Figures, the ring 32 is shown as beingequipped with a cam slot 46 through which a peg 48 on the guidewire 40passes before becoming latched with further rotation of the guidewire40, while the second ring 34 is depicted as having internal threads 50that threadably mate with external threads 52 on the end of theguidewire 42, as is a standard current practice in the cardiovascularfield. The ring 34 and its internal threads 50 are coaxially alignedwith the axis of the central body 16, as is the ring 32. The guidewire40 has a tubular shape through which the guidewire 42 is able toreciprocate. The entire guidewire assembly is shown in FIGS. 5, 7, and 8as being disposed in a delivery catheter 44 of a type known in the art.The configuration of the anchor 10 allows the anchor 10 and its implant12 to be inserted inside the delivery catheter 44 and then positionedfor insertion into the wall 14, and permits multiple tries to secure theanchor 10 in the desired location before deploying the arms 22 andarcuate members 24 and final detachment of the guidewires 40 and 42.

According to one aspect of the invention, one or more of the followingcomponents of the anchor 10 can be integral portions of a monolithicbody: the central body 16, arms 22, arcuate members 24, first ring 32,second ring 34, and struts 36. For example, the central body 16, arms22, arcuate members 24, first ring 32, and struts 36 can be formed froma monolithic body, while the second ring 34 is formed separately suchthat completing the anchor 10 requires only attachment of the secondring 34 to the struts 36, for example, by welding or anothermetallurgical joining technique. A preform 54 for this purpose isdepicted in FIG. 6. Another and potentially preferable approach isrepresented in FIG. 15, which shows the central body 16, arms 22, struts36, and second ring 34 as integral parts of a first monolithic body, andthe arcuate members 24 and first ring 32 as integral parts of a secondmonolithic body that is joined or coupled to the first monolithic body.As represented in FIG. 15, the first ring 32 is telescoped over thesecond ring 34, and the rings 32 and 34 are interconnected with springlatches 64, though joining by other means is also possible, such as bywelding. As such, the spring latches 64 are used to directlyinterconnect the rings 32 and 34, instead of through the arcuate members24, central body 16, and struts 36 as done in the embodiment of FIGS. 1through 5. In effect, the assemblage of the central body 16, struts 36,and rings 32 and 34 are functional equivalents of the central body 16 ofFIGS. 1 through 5, such that the arcuate members 22 extend substantiallyradially from an end (second end 20 in FIGS. 1-5) of the central bodythat is defined by the ring 32 in FIG. 15.

Many existing medical implantable devices for use in the heart utilizeNITINOL®, a “shape memory” nickel-titanium alloy that enables anumbrella-like structure folded inside a catheter for delivery to laterautomatically expand once outside the catheter for implantation. In apreferred embodiment, the anchor 10 is formed of NITINOL or anothersuitable shape memory material. According to another preferred aspect,the anchor 10 can be manufactured primarily by laser cutting techniquesperformed on solid tubes of a shape memory material, rather thanprimarily using welding techniques as typically done in the prior art.Fabrication of the anchor 10 using laser cutting techniques provides atleast two important advantages. First, the reliability of the anchor 10is much higher since its components (body 16, arms 22, arcuate members24, ring 32, struts 36, and/or fingers 38) are integral portions of oneor a limited number of monolithic metal pieces. Welded joints possesshigher risk of failure than that possible with the preferredconstructions for the anchor 10. Secondly, the cost of manufacturing canbe significantly lower than would be possible if relying primarily onwelding to form the anchor 10.

In practice, a NITINOL tube can be cut by laser alone to form thepreform 54 depicted in FIG. 6, or to form two preforms for the twosubcomponents for the embodiment depicted in FIG. 15. The laser cuttingoperation can be performed as an automated process based on drawingfiles using commercial mechanical design software. The tubular-shapedpreform or preforms are then formed into a 3-D structure with shapememory by being placed in a mechanical jig and heated to an appropriatetemperature to store the shape into the memory of the NITINOL material.In the case of the preform 54 of FIG. 6, the second ring 34 is thenwelded to the ends of the struts 36 to yield the structure shown inFIGS. 1 through 5. These welds are the only welds required by the anchordesign of FIGS. 1 through 5. In the case of the embodiment of FIG. 15,welding can be completely eliminated as a process step.

A key parameter of any wireless, implantable system is the communicationdistance (both tele-powering and telecommunication) between the implantand the readout handheld unit. Since the anchor 10 may be formed of ametal such as NITINOL, there exists a potential that such a metallicanchor could adversely affect (reduce) the communication distancebetween the implant 12 and the handheld unit (not shown) by actingsimilar to a Faraday cage. Tests performed using metal implantsindicated that telemetry communication distances can be reduced by abouttwo-thirds, such that placing an implant using RF/electromagnetictelemetry inside a metal anchor would not be expected to achievereasonable performance.

To overcome this problem, the anchor 10 is configured to avoid theprimary causes of reduced communication distances. Attenuation wasdetermined to depend on parameters including the number of metal loops,the orientation of the loops, and whether the loops are arranged in sucha manner as to form a mesh or cage. Fewer numbers of metal loops wereassociated with longer communication distances. Furthermore, metal loopsthat are arranged in parallel to the implant communication coil (with orwithout a ferrite core) were found to not adversely affect thecommunication distance, while metal wires oriented perpendicular to theimplant communication coil (with or without a ferrite core) were foundto greatly reduce such magnetic fields. The anchor 10 of the presentinvention comprises few loops which are properly oriented and do notform a mesh. As seen in the Figures, the anchor 10 is able to makesatisfactory use of only three sets of arms 22 and arcuate members 24.Furthermore, as discussed above, the arms 22 and arcuate members 24 ofthe anchor 10 are oriented to entirely lie within three planes whoseintersection coincides with the axis of the anchor 10 and its implant12. In this manner, the anchor 10 of this invention renders practicalthe use of small implants across long communication distances using ametallic anchor.

The anchor 10 may be employed to locate the implant 12 in variousplaces, depending on the physiological parameter of interest. For thetailored treatment of chronic heart failure, LVEDP and/or MLA pressureare of most importance, and therefore the left chambers of the heart orimmediately attaching vessels are among preferred locations for theimplant 12. Because the number of implants is not practically limited bythe technology, multiple locations for blood pressure measurement areeasily established, including all chambers of the heart, major arteriesand appendages. The preferred waveforms to monitor for CHF applicationsare the pressures of the left atrium. The monitored waveforms mayinclude but not limited to complete detailed LA waveform, particularlyaccurate MLA pressure, real time, and continuous. It should be mentionedthat some aspects of the anchor 10 described above will allow pressuremeasurements of the right atrium (by locating the pressure sensor at theend of the implant 12 facing the right atrium) or both right and leftatriums (for example, using two pressure sensors, one at each end of theimplant 12), or direct differential pressure measurement between theright and left atrium (again, for example, using two pressure sensors,one at each end of the implant 12). In addition to or instead ofpressure, other parameters can easily be monitored using an implantdelivered and placed with the anchor 10. Such parameters include but arenot limited to blood chemistry, oxygen level, etc. For example, ahydrogel film (with selectivity to different elements) can be placed ontop of a pressure sensor to measure the presence of elements that causethe hydrogel to expand, thereby applying pressure to the pressuresensor.

Thrombogenicity is the primary concern when considering a device forimplantation in the left side of the heart, due to the possibility ofthrombi reaching the brain. In order to assure such high-level ofnonthrombogenicity, the present invention is able to reduce such risksthrough proper anchor shape, anchor location, and delivery method.

Thrombogenesis can be caused by direct chemical interaction with animplant or anchor, and by blood flow turbulence resulting from implantgeometry. Regarding the former, the materials for the implant 12 andanchor 10 must be selected to be either biocompatible or the implant 12and anchor 10 must be covered by biocompatible materials. As to thelatter, the present invention provides an anchor configuration andplacement capability that greatly reduces protrusion of the implant 12and anchor 10 into the blood flow path of the left atrium to a minimumlevel, and also provides a hydrodynamic sensor profile that is minimallydisruptive to surrounding blood flow. The implant 12 can be preferablyplaced with the anchor 10 of this invention at two desirable locations:the atrial septum and left atrial appendage. The atrial septum isbelieved to be preferable for locating the anchored implant 12. Itshould be emphasized that, while the implant may be long length (e.g.,lengths greater than 10 mm), the anchor 10 is configured so that only asmall portion (e.g., less than 2 mm) of the implant 12 is exposed to theleft side of the heart; the rest of the implant 12 is in the septum walland the right atrium. The pressure sensor is placed at or near the endside of the implant 12 that is exposed to the left side. A preferredlocation for the pressure sensor is believed to be on the front flatside of the cylindrical implant 12 shown in the Figures, so that only asmall portion of the implant 12 will be above the surface of the leftside of the heart. Subsequent cell growth over the top of the smallexposed area of the implant 12 will further reduce the risk ofthrombogenicity.

If placed in the atrial appendage, the implant 12 may be anchored byexpanding the anchor 10 and then occluding the appendage. In this case,thrombi formation on the distal end (opposite from sensor) of theocclusion device would not pose a risk to the patient, as evidenced byprevious left atrial appendage devices that have been introduced forthis very purpose.

A reason for preferring placement in the atrial septum is that thereexists FDA-approved, commercially-available medical devices for chronicimplantation in this location. These devices, for example, are used toocclude atrial septum defects and other vascular holes. The implant 12can be anchored to the atrial septum with similar techniques asFDA-approved, commercially-available devices such as the AMPLATZER®family of devices commercially available from AGA Medical, or theCardioSEAL commercially available from NMT Medical. These devices havebeen shown to be suitable for cardiovascular implantation. As a result,one may take advantage of this existing infrastructure, includingstandard practices of delivering cardiovascular implants. Anotheradvantage of placing the implant 12 within the wall of the atrial septumis that the potential adverse confounding effects of the musclecontraction on the sampled pressure measurements will be considerablyreduced.

Delivery of the implant 12 with the anchor 10 demands suchconsiderations as safety, minimal invasiveness, suitability as anoutpatient procedure, ease of operation, preferable use of existingpractices, minimum training for the physician/technician, and theability to allow multiple tries before deploying and releasing theanchor 10. The preferred delivery method for the anchor 10 is believedto be by catheter delivery, such as with the delivery catheter 44depicted in FIG. 5. To minimize catheter diameter, the implant 12 ispreferably small and thin. Delivery and placement of the anchor 10 isable to make use of standard current practices in the cardiovascularfield to reduce both time and cost of R&D and manufacturing, createcomfort and confidence in cardiologists, and make FDA process easier.The anchor 10 is configured so that, after it is inserted into thecatheter 44, the diameter of the folded anchor 10 is equal or as closeas possible to the diameter of the original tube from which the preform54 was laser cut. This approach renders the smallest possible diameterof the delivery catheter 44.

In the preferred configuration shown in FIG. 5, the delivery catheter 44has the two guidewires 40 and 42 discussed above. The inner guidewire 42is coupled to the second ring 34, while the outer tubular guidewire 40is coupled to the first ring 32 of the anchor 10, as seen in FIG. 5.FIGS. 9 through 13 represent a series of steps depicting the procedurefor delivering and implanting the anchor 10 and implant in the atrialseptum 14. Using a standard cardiology guidewire via a standardprocedure (not shown), the delivery catheter 44 is placed through theatrial septum 14. The anchor 10 is then inserted into the catheter 44.By slightly pulling the outer guidewire 40 away from the inner guidewire42, the anchor 10 is straightened and roughly reacquires the originalshape of its preform 54. FIG. 9 portrays this point of the deliveryprocess, in which the pads 26 of the arms 22 protrude from the catheter44. The anchor 10 is then pushed through the catheter 44 by grasping andpushing both guidewires 40 and 42 at the same time. The anchor 10 ispushed until the arms 22 are completely free of the catheter 44, suchthat the shape-memory property of the anchor material causes the arms 22to expand with the pads 26 projecting back toward the atrial septum 14as seen FIG. 10. Both guidewires 40 and 42 are then pulled back untilthe pads 26 rest on the left side of the atrial septum (FIG. 11). Thecatheter 44 is then retracted, causing the arcuate members 24 to bereleased on the side of the septum 14 opposite the arms 22. As with thearms 22, the shape-memory property of the anchor material causes thearcuate members 24 to expand so that their legs 28 project toward theatrial septum 14 as seen FIG. 12. The outer guidewire 40 can then bereleased by holding the inner guidewire 42 steady while the outerguidewire 40 is decoupled (FIG. 13). Finally, the inner guidewire 42 canbe decoupled from the second ring 34, resulting in what is depicted inFIG. 14.

As an alternative to the above, the guidewires 40 and 42 may be latchedto the rings 32 and 34 by means of flexible spring latching fingers 60and 62 permanently attached to the guidewires 40 and 42, as depicted inthe embodiment of FIG. 15. The latching fingers 60 and 62 are shown asbeing adapted to mate with corresponding recesses within the rings 32and 34, respectively. FIG. 15 shows the latching fingers 60 and 62 asbeing held in the latched position by a central core element 58 heldaxially within the center of the guidewires 40 and 42. The core element58 prevents the latching fingers 60 and 62 from disengaging the rings 32and 34 during insertion of the anchor 10 and implant 12. The coreelement 58 can also be used to temporarily couple the rings 32 and 34together during implantation, allowing the guidewires 40 and 42 toindividually support the rings 32 and 34 while displaced axially apartfrom each other. The rings 32 and 34 are not locked together with thespring latches 64 until the arms 22 have been deployed. When this hasbeen accomplished, the guidewire 40 can be used to push the ring 32forward to radially spread the arcuate members 24 (which arecantilevered, in contrast to the embodiment of FIGS. 1-5), telescope thering 32 over the ring 34, and finally latch the rings 32 and 34together. With this approach, the guidewires 40 and 42 are decoupledfrom the rings 32 and 34, respectively, by retraction of the centralcore element 58 within the guidewires 40 and 42. As the core element 58is withdrawn, the latching fingers 60 and 62 collapse radially inwardtoward the central axis of the guidewire assembly and disengage fromrings 32 and 34.

In view of the above, the operator has the option to retry placing theanchor 10 and implant 12 any number of times before releasing the anchor10 with the outer guidewire 40. The preferred use of two guidewires 40and 42 is believed to be uncomplicated and readily within the skills ofthe ordinary cardiologist. Nonetheless, those skilled in the art willappreciate that the anchor 10 and its implant 12 could be delivered andplaced with a single guidewire set.

In addition to the delivery and anchoring of wireless implanted medicaldevices, the anchor 10 and delivery method of this invention can beutilized for non-wireless applications. For example, a pressure sensor(or any other type of sensor) located in the left atrium (or elsewhere)can be provided with a communication connection to other medical devices(such as, but not limited to, pacemakers) from the right atrium side ofthe anchor/implant. Potential communication connections include, but arenot limited to, electrical wires, pacemaker leads, flexible cables,optical connectors, ultrasonic pads, and electrophysiology signals.Hermetic electrical connection pads (instead of or in addition to apressure sensor) can be provided from inside the implant 12 to itsexterior. Such pads can be used to provide electrical connections toother medical devices, e.g., pacemakers, or provide electricalconnections to other sensors (e.g., blood chemical sensors), which aremade independently of the anchor 10 and implant 12. Preferred locationsfor these pads are believed to be either of the flat ends of thecylindrical implant 12 shown in the Figures, for locating the pads inthe left side, right side, or both sides of the heart.

While the invention has been described in terms of certain embodiments,it is apparent that other forms could be adopted by one skilled in theart. Therefore, the scope of the invention is to be limited only by thefollowing claims.

1. A method of placing a medical implant, the method comprising thesteps of: inserting a medical implant (12) through an opening (17) in abody portion (16) of an anchor (10) from which a set of arms (22)extend; coupling at least a first guidewire (40) to a first portion (32)of the anchor (10) and coupling at least a second guidewire (42) to asecond portion (34) of the anchor that is disposed between the body andfirst portions (16,32) of the anchor (10), the anchor having an axisthat is coaxial with the first and second guidewires; placing an end ofa delivery catheter (44) through an internal wall of a human body;inserting the anchor in the delivery catheter with the first and secondguidewires so as to place the anchor within the internal wall, cause thearms (22) of the anchor to protrude in a first direction from the end ofthe delivery catheter, and then cause the arms (22) to extendsubstantially radially from the anchor; retracting the first and secondguidewires through the delivery catheter in a second direction oppositethe first direction, the first and second guidewires being retracted sothat the arms (22) of the anchor contact a first side of the internalwall; retracting the delivery catheter to release a plurality of members(24) coupled to the first portion (32) of the anchor (10), whereinreleasing the members (24) causes the members (24) to extendsubstantially radially from the anchor (10), causes a leg (28) of eachof the members (24) to move in the first direction into contact with anoppositely-disposed second side of the internal wall so as to secure theanchor and the medical implant received therein to the internal wall,and causes the first portion (32) of the anchor with the first guidewire(40) coupled thereto to travel toward the second portion (34) of theanchor; decoupling the first guidewire (40) from the first portion (32)of the anchor; and then decoupling the second guidewire (42) from thesecond portion (34) of the anchor.
 2. A method according to claim 1,wherein the body and first portions (16,32) of the anchor areinterconnected by the members (24), and the members are collapsed beforeplacing the anchor in the delivery catheter by moving the first andsecond guidewires in opposite directions.
 3. A method according to claim1, wherein the body and second portions (16,34) of the anchor arerigidly interconnected prior to inserting the medical implant and definean enclosure that contains the medical implant after the medical implantis inserted.
 4. A method according to claim 1, where the opening (17)through which the medical implant (12) is inserted into the body portion(16) is located at a first end (18) of the anchor (10).
 5. A methodaccording to claim 4, further comprising the step of securing themedical implant within the anchor with fingers located on the first end(18) of the body portion (16).
 6. A method according to claim 4, whereinthe arms (22) extend from the first end (18) of the anchor.
 7. A methodaccording to claim 4, wherein the first portion (32) of the anchor (10)is at an oppositely-disposed second end of the anchor (10).
 8. A methodaccording to claim 1, wherein the first and second guidewires (40,42)are coupled to the first and second portions (32,34), respectively, withmeans (46,48,50,52) comprising at least one element selected from thegroup consisting of cam slots, threads, snaps, snap latches, latchfingers, spring latches, latch fingers with a catheter sheet forreleasing the latch, guidewires, catheters, dissolvable glues, temporaryglues, thermal glues, heated shape memory latches, unheated shape memorylatches, heated mechanical means, piezoelectric release systems,hydraulic coupling systems, pneumatic coupling systems, and magneticcoupling systems.
 9. A method according to claim 1, wherein the firstand second portions (32,34) comprise coaxial axially-spaced first andsecond rings (32,34), respectively.
 10. A method according to claim 9,wherein the first guidewire (40) is coupled to the first ring (32) witha cam slot (46) and the second guidewire (42) is coupled to the secondring (34) with threads.
 11. A method according to claim 1, wherein thefirst and second guidewires (40,42) are decoupled from the first andsecond portions (32,34) of the anchor by moving a member (58) disposedwithin the first and second guidewires.
 12. A method according to claim11, wherein fingers couple the first and second portions to the firstand second guidewires during the insertion step, and movement of themember releases the fingers so as to decouple the first and secondportions from the first and second guidewires.
 13. A method according toclaim 1, wherein the first and second portions are latched togetherafter the arms contact the first side of the internal wall.
 14. A methodaccording to claim 1, wherein the medical implant is a cardiovascularimplant and the internal wall is a portion of a cardiovascular organ.15. A method according to claim 14, wherein the internal wall is anatrial septum.
 16. A method according to claim 14, wherein placement ofthe medical implant is used in a procedure performed to diagnose,monitor, and/or treat a cardiovascular disease.
 17. A method accordingto claim 1, wherein placement of the medical implant is used in aprocedure performed to diagnose, monitor, and/or treat an internalorgan.
 18. A method according to claim 1, wherein the implant isreceived within and secured to the body portion (16), and the implant iscommunicatively connected to a medical device.
 19. A method according toclaim 18, wherein the medical device is a pacemaker.
 20. A methodaccording to claim 18, wherein the implant is communicatively connectedto the medical device by a communication connection selected from thegroup consisting of electrical wires, pacemaker leads, flexible cables,optical connectors, ultrasonic pads, and electrophysiology signals.